1. Field of the Invention
The invention relates to communications, and more particularly to multi-media communications over Internet Protocol (“IP”).
2. Background Art
Session Initiation Protocol (“SIP”) is a protocol that allows two or more parties on an Internet Protocol (“IP”) network to engage in multimedia sessions. SIP is a media agnostic protocol that allows any media, such as text, voice, video or any combination to be exchanged between parties.
SIP features and operations are described in Internet Engineering Task Force (“IETF”) Request for Comment (“RFC”) 2543, SIP: Session Initiation Protocol. In general, SIP is an application-layer control protocol that can establish, modify and terminate multimedia sessions. In the voice context, a session using SIP can be considered a call.
These multimedia sessions include multimedia conferences, distance learning, Internet telephony, such as voice over Internet Protocol (“VOIP”) and similar applications. SIP can invite both persons and devices, such as media storage service devices to participate in a session or call. SIP can invite parties to both unicast and multicast sessions. SIP can be used to initiate sessions as well as invite members to sessions that have been advertised and established by other means.
The SIP protocol provides a robust signaling protocol that takes advantage of the growing availability of IP networks, such as the Internet and other wide and local area networks often used within corporate communication networks. An implementation challenge associated with the SIP Protocol is how to effectively integrate the use of the SIP protocol with existing telecommunications switches, including private branch exchanges (“PBXs”) and other network elements.
Many existing communications network elements have call processing software modules that provide call setup and feature control based on traditional signaling, such as multi-frequency (“MF”), dual tone multi-frequency (“DTMF”), Integrated Services Digital Network (“ISDN”) and Signaling System 7 (“SS7”), found in public switched telephone networks (“PSTN”) that support plain old telephone service (“POTS”) and advanced services often associated with PBXs and business services. These call processing software modules are sophisticated and have evolved over many years of use and development to eliminate software glitches and optimize performance. They support a multitude of call setup processes, call services and call feature interactions. Furthermore, end user customers have come to rely on many of the call features supported by traditional signaling methods. Developing entirely new call processing software modules to support the SIP protocol would not effectively utilize the years of development of existing call processing software modules, particularly when a network element must continue to support legacy telephones and SIP endpoints, which may include IP telephones, computers and other communications devices.
What are needed are systems and methods that can effectively use proven call processing software modules, while supporting and integrating the SIP protocol.